Non-microphonic tube construction



May 25, 1965 L. FEINSTEEN NON-MICROPHONIG TUBE CONSTRUCTION FiledJuly 1. 1952 6 0 44 0 W4 M 7 a 7 eu M 3m gr 4 7%; x

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INVENTOR LESTER FEINSTEIN BY lum/ ATTORNEY United States Patent3,185,$83 NUN-MZCROPHONIC TUBE CGNSTRUETEGN Lester Feinstein, Bellerose,N352, assignor, by mesne assignments, to Sylvania Electric Products Inc,Wilmington, DeL, a corporation of Delaware Filed July 1, 1952, Ser. No.296,631 8 (Jlaims. (Cl. 313-269) This invention relates to electrondischarge devices and more specifically to improved structures for usein multielectrooe electron tubes.

In the design of vacuum or gas filled electron tubes a major concern hasbeen the elimination of microphonism in the construction of the tube.The so-called microphonism occurs due to structural weaknesses in thetube which give rise to variations in orientation or the spacing betweenthe elements of the tube. Microphonism may occur, for example, as aresult of filament or cathode vibration which imparts a modulation tothe electrons passing from the cathode to the anode of the tube as aresult of displacement of all or a portion of the filament or cathode.Similarly, microphonism may occur as a result of vibration of thecontrol grid structure which, in turn, modulates the electron stream andgives rise to unwanted noise output from the tube. A third source ofmicrophonism is in the anode itself which if it is not built withsufficient rigidity, may produce modulation of the elec tron stream dueto variations in the current collected by the anode. Microphonism mayalso be caused by several of the above eiiects operating together toproduce varia tions in electrode spacing with consequent variation inoutput voltage.

It is an object of this invention to minimize microphonism in electrontube structures.

It is a further object of the invention to provide a rigid constructionwith a high strength-weight ratio.

It is a still further object of the invention to provide an improvedelectrode support or mount in an electron tube.

It is a still further object of the invention to provide an anodestructure for an electron discharge device having a high strength toweight ratio.

An even further object of the invention is the provision of a filamentstructure for use in electron discharge devices which is accessible foreasy assembly and adjustment and which is minimally responsive tovibration.

A further object of the invention is to provide a vacuum tube electrodemount which is extremely strong and is resistant to both bending andtorsion forces.

A still further object is the reduction of grid-plate capacitance intube structures having rugged elements.

A still further object is the reduction of electrode lead inductance.

The above objects and others, which will appear as a result ofconsideration of the drawings and below appended description of theinvention, are achieved by providing a vacuum tube mount structureemploying a centrally located anode surrounded by one or more grids, andhaving an outwardly disposed cathode or filament. A preferred embodimentof the invention is illustrated in the drawings in which:

FIG. 1 is a view in longitudinal cross-section of an electron dischargedevice embodying the invention.

FIG. 2 is a perspective view of the mount structure employed in thedischarge device of FlG. 1.

Referring now to FIG. 1, it will be seen that a vacuum tube mountstructure is contained Within the cylindrical walls of glass envelope 2,and that connections are made to the electrodes in the mount by means ofleads 4 projecting from and sealed through the wall of glass water base6. The mount structure within the envelope is supported in place bywelding inner ends of leads 4 to exten- 3,l85,883 Patented May 25, 1965sions of grid side rods 8 which are spaced to provide four rectangularlydisposed side supports for grid 22. Located near either end of grid 22and extending transversely thereof are upper spacer disc 19 and lowerspacer disc 11 which are made of an insulating materal such as mica.Spacer members it and 11 serve in turn to support anode side rods 12,tensioner support side rod 14, filament tie strips 16 and filamentdampers 18.

Referring now to FIG. 2, in which the numerals used in FIG. 1denurnerate the same parts, it will be seen that anode side rods 12support hollow rectangular anode 15 at the midpoints of the shortersides of anode 15. Anode side rods 12 are preferably welded to anode 15.Grid 22 is also a hollow rectangular tube, preferably of conductivesheet material such as sheet metal, and is welded at its four corners togrid support rods 8. Opposite faces 24 of grid 22 are provided withlongitudinal rectangular apertures or slots 26 over which grid wires 28are fastened. In the preferred embodiment of the invention, grid wires23 are spaced parallel to each other across the shortest dimension ofgrid aperture 26 and are fixed to faces 24 of grid 22 by Welding orother techniques commonly known in the art. The spacing of the gridwires and their diameter may be chosen according to well knownprinciples to provide a given type of electrical characteristic byinterstitially dividing the grid apertures 26 with conducting elements28.

The electron source for the tube is filament 30 which is attached tolower mica 11 by means of filament anchoring strap 16 and passes throughmica ll at wedge shaped openings 32. The filament wire is retained in aposition parallel to and centered adjacent to faces 24 of grid 22,passing through Wedge shaped opening 34 in upper mica l0 and overtensioning spring $6 at the upper end of the resulting filamentaryconfiguration being generally U shape and disposed outwardly of theelectrodes. Filament tensioning spring 36 is provided with hook 355 toreceive filament 3d and derives its support from horizontal pivot rodtil, which, in turn, is supported at its center by tension support plate42, the latter being welded to the upper end of tension support side rod14. End loops 44 of filament support spring 36 are wound around pivotrod 40 and returned in the general direction of hook 38 to bear onledges 46 of filament tensioning support plate 42. By this means spring36 works against filament 3t) keeping it under tension.

Damping or stabilizing for filament 3% is provided along its activelength by means of damping bars or elements 1% which are of a generallyL-shaped configuration, one end of bar 18 being anchored in lower mica11 and the horizontal portion of the bar extending generally parallel toface 24 of grid 22., and outwardly of filament 30 so as to exert aslight pressure thereon. In order to minimize heat losses, an insulatingcoating (not shown) of low heat conductivity is applied to the outersurfaces of filament damper rods 18 at their points of contact withfilament fill. The location of the contact between dampers l8 andfilament 3t and the force to be applied thereby will, of course, bedetermined by criteria already well known in the art and will ordinarilybe accomplished at some point along the filament adjacent to the anode.

A typical design of the mount described above employs the followingdimensions: spacing between filament 30 and face 24 of grid 22 is about.006 inch and between grid 24 and plate 15 about .815 inch. According tocurrent design practice the effective area of the filament as projectedon the grid is such that the filament is at the apex of a triangle, theopposite side of which is the Width of the plate, in this instance about.090 inch. Accordingly, with the spacings given above, the opening inthe grid should be a minimum of .012 inch in width but,

'the grid structure is considerably enhanced.

in order to allow for fringe etfects, the grid width may be as much as.030 inch. The grid frame itself has a depth of about .135 inch and aWidth on the slotted sides of about .155 inch, its length beingdetermined by ordinary design considerations. is such a small portion ofthe total Width of face 24 of the grid member 22, it will be seen thatthe rigidity of Broadly speaking, thestrength of the grid frame variesas the ratio of the cube of the width of face 24 to the cube of theWidth of slot 25. It should be noted, too, that the rectangular form ofboth grid 22 and anode 15 contributes substantially to the rigidity ofthese members, thus reducing any tendency of the members to contributeto microphonism in the final tube structure.

Vibration of the filament is minimized by utilizing the structureillustrated and by individually setting the tension up on each side offilament 39 by means of dampers 18 at the time of fabrication of themount prior to its bly operation.

It will be apparent to the reader that many changes I may be made to thedetail of the structural principles employed Without deviating from thespirit of the invention. For example, the use of other types ofapertures than the slot in the grid may be desirable, as Well as otherconfigurations than rectangular for the grid and anode bodies.Similarly, the anode and grid extensions which traverse the insulatingspacer members may be made integral with those electrodes, rather thanas side rods as here shown.

For the above reason it is desired that the below appended claims beconstrued in keeping with the spirit of the invention rather thanlimited to the illustrative embodiment detailed above.

What I claim is:

1. An electron discharge device having an envelope enclosing arectangular anode, a rectangular grid of conductive sheet materialsurrounding said anode and having a number of electron apertures, and anelectron source adjacent to said apertures, said grid including anelongated tubular portion of high strength to Weight ratio.

2. An electron discharge device having an envelope enclosing arectangular anode, an elongated tubular grid of sheet conductivematerial rectangular in cross section and surrounding said anode, saidgrid having a number of longitudinally elongated electron apertures of awidth substantially less than the width of the anode, and a number ofelectron sources adjacent to said apertures.

3. An electron discharge device having an envelope enclosing anapertured tubular grid, longitudinal support members extending from saidgrid and anchored to said envelope, an anode, a source of electrons, andtransverse insulating members disposed at either end of said gridstructure and supported thereby, said transverse members Inasmuch as thegrid slot width.

longitudinally supporting said anode member within said grid structureand said electron source on the side of said grid member away from saidanode member.

4. An electron discharge device having an envelope enclosing asubstantially rectangular tubular grid of conductive sheet material andhaving longitudinal apertures disposed at intervals around the peripherythereof, a substantially rectangular tubular anode, an electron source,a number of side rods fastened in corners of said grid and extendingbeyond the ends of said grid, and a pair of transverse insulatingmembers supported by said side rods at either end of said gridand'projecting laterally with respect thereto, said transverse memberssupporting said anode centrally within said grid and supporting saidelectron source oppositesaid apertures in said grid.

5. The discharge device of claim 4 in which a pair of said longitudinalapertures are oppositely located on said anode and said electron sourceis a substantially U-shaped filament each leg of which passes adjacentto one of said apertures.

6. The discharge device of claim 4 in which said longitudinal aperturesare divided into groups of smaller apertures by a number of conductingelements placed thereacross. V

7. The discharge device of claim 4 in. which said transverse membershave openings near either extremity and said electron source comprises afilament passing through said openings and maintained thereby in spacedrelation adjacent said aperture.

8. An electron discharge device having a number of electrodes includina. tubular grid, lateral supporting and insulating members supported bysaid grid, an anode supported within said grid by said insulatingmembers, an envelope surrounding said electrodes, and lead-in conductorssealed through said envelope and projecting rigidly towards saidelectrode structure, said so-supported assembly being anchored againstlongitudinal motion to a number of said lead-in conductors.

References Cited hythe Examiner UNITED STATES PATENTS DAVID J. GALVIN,Primary Examiner.

RALPH G. NILSGN, ELI I. SAX, JAMES L. BREWRINK, CHESTER L. IUSTUS,Examiners.

1. AN ELECTRON DISCHARGE DEVICE HAVING AN ENVELOPE ENCLOSING ARECTANGULAR ANODE, A RECTANGULAR GRID OF CONDUCTIVE SHEET MATERIALSURROUNDING SAID ANODE AND HAVING A NUMBER OF ELECTRODE APERTURES, ANDAN ELECTRON SOURCE ADJACENT TO SAID APERTURES, SAID GRID INCLUDING ANELONGATED TUBULAR PORTION OF HIGH STRENGTH TO WEIGHT RATIO.